In drilling the pronuncation of a foreign language, a trainee often asks a person who speaks the foreign language as a mother tongue (hereinafter referred to as "native speaker") to evaluate his pronunciation. Further, the trainee can drill by himself using cassette tapes, videotapes, record disks, and books that are commerically available.
Evaluation of pronunciation by the native speaker involves difficulty in that the native speaker finds it difficult to explain subtle difference of pronunciation to the trainee and further that the native speaker seldom lives near the trainee. When cassette tapes or the like are used, the drill chiefly consists of a repetition of an exercise based upon hearing judgment. The image provided by a videotape is effective for explaining the word spelling, phonetic symbols, mouth shape, tongue position, and scenery, but is not very helpful for drilling pronunciation; i.e., evaluation is solely based upon the hearing sense of the trainee. In short, cassette tapes and the like do not precisely explain how the trainee can pronounce the words correctly. In other words, the trainee finds it difficult to known how close his pronunciation is getting to correct pronunciation and thus enjoys limited success in learning the language being studied.